**1. Introduction**

Energy has been a fundamental driver of global economies in order maintain development in almost any industry. It is compulsory that the sources of energy must be maintained and continue developing to meet the demand. With fossil fuel continuing to be proven to be detrimental to the environment, solar energy is continuing to become a modern, growing, and potential source of renewable energy. According to the International Energy Agency (IEA) in 2015, the consumption of fossil fuels coming from coal, oil, and natural gas accounts for 81.6% of the total energy consumption amongs<sup>t</sup> the 38 leading countries. From the same data, wind, and solar energy only accounts for 1.5% of the energy consumption [1]. As also shown in Figure 1, solar energy has the highest development compared to other renewable energies such as hydropower, onshore and offshore wind energy, and bioenergy [2]. According to NASA's physics and astronomy calculations, solar energy is still available for about 6.5 billion years before the sun fades away, which means that the energy source can be utilized for a longer and more durable time before it is projected to deplete [3].

*Energies* **2020**, *13*, 4066

**Figure 1.** Comparison of different renewable energy sources [4].

Solar energy takes the direct sun rays from the sun and transforms them into usable energy consumed for many purposes. The major limitations of solar energy include geographical conditions, high dependency on technology development, large installation area with a high initial cost. Additionally, with such limitations come additional, big environmental changes where modifications could leave an impact on local ecosystems should the development a plant be initialized with the trend of sustainable development, and maintaining the balance of the triple bottom line of environmental, social, and economical elements must be considered [5].

Solar energy is still not a popular energy source amongs<sup>t</sup> the economic and social development of the provinces in the Mekong Delta region, Vietnam. However, according to Vietnam Academy of Science and Technology (VAST), Vietnam is one of the potential countries for solar energy development when looking at the data for the amount of sun rays the world receives annually, shown in Figure 2 with a second highest overall evaluation of 4–5 Kwh/m<sup>2</sup>/day [6].

**Figure 2.** Average amount of potential solar energy output [6].

In fact, if more than 50% [7] of the energy supply for a national electricity system is imported from other countries, the risk of energy unavailability will be extremely high. Once that supply is depleted or affected by natural disasters, accidents, armed conflicts, sabotage, policy changes or strikes within coal mines, energy security will be directly affected. Besides, the coal transportation from a remote area to the electric production factory, which is done mainly by sea, also has many potential implications for the environment, social security, and economy. The pollution of dust, noise, and ash accumulation from the operation of coal-fired power plants can cause frustration in the local community and sow the seeds for protests, creating long-term instability in terms of social security [8]. Located in the tropical and monsoon region, with an abundant solar energy, the Mekong Delta of Vietnam is entering a period of strong solar power development. Solar energy has been selected as one of the major alternative renewable energy sources in the energy development strategy of the Mekong Delta region. Solar Radiation Maps of Vietnam is shown in Figure 3.

**Figure 3.** Solar Radiation Maps of Vietnam [9].

Currently, there is very little research for developing a solar power plant in Vietnamese Mekong Delta region. Determining an optimal location, which is sustainable and satisfies the triple bottom line

concepts, is essential for the growth of the country's power supply and alleviates the environmental damage from fossil fuel consumption by promoting a renewable alternative energy supply. Therefore, this problem is tackled as a Multi-Criteria Decision Making (MCDM) problem that requires both quantitative and qualitative information to be considered. The MCDM problem is commonly defined as determining an optimal decision based on a finite set of available decision alternatives with multiple, and potentially conflicting, criteria.

As mentioned, the purpose of this paper is now to propose a suitable MCDM methodology for localizing and selecting an optimal area in Vietnam in developing a solar power plant. In the next section, the literature will be presented to discuss the first stage of the paper. Discussions and results' analysis are explained towards the end of the paper.
